"Baby" is a song by Canadian singer Justin Bieber featuring American rapper Ludacris. It was released as the lead single on Bieber's debut studio album, My World 2.0. The track was written by the artists alongside Christina Milian and producers Tricky Stewart and The-Dream.

Christopher Brian Bridges, known professionally as Ludacris, is an American rapper and actor. Born in Champaign, Illinois, Ludacris moved to Atlanta, Georgia, at age nine, where he first began rapping. Starting out with a brief stint as a DJ, he formed his own record label, Disturbing tha Peace in the late 1990s to independently release his debut studio album Incognegro (1999). The album was re-released by Def Jam Recordings as his major label debut, Back for the First Time (2000) after its single, "What's Your Fantasy", became a top 40 hit on the Billboard Hot 100. The latter album peaked at number four on the Billboard 200 and spawned his second top 40 single, "Southern Hospitality".